Aerators are commonly used for maintaining landscaped ground surfaces including turf. The term “turf” refers to grass and other material which is specifically grown for sporting activities and is used, for example, to form golf course greens. Aerators on these types of surfaces have a coring head with tines that repeatedly penetrate the ground surface, forming a plurality of holes so that the ground surface is aerated, to improve growth of the grass or other material and enhance the condition of the surface for playing purposes.
In conducting this type of aeration of turf surfaces, the neatness of the holes made by the aerator tines can significantly affect the overall result. For example, in the case of golf greens and the like where the vegetation is short, a hole with rough edges or too large a hole can cause spot erosion, resulting in an undesirable dimple in the ground surface. This effect is aggravated when forward movement of the aerator differs from the speed of the coring head over the ground surface, causing the tines to rake across or break the ground surface.
To minimize rough edges of the holes, aerators may be designed to keep the tines substantially vertical for entry and withdrawal from horizontal ground surfaces. For example, aerators may have flywheels that drive the upper ends of tine supports in a circular path, and the lower ends in a reciprocating motion of repeated penetrations into the ground. Link arms can pivot to compensate for forward motion of the machine. At each part of the cycle when the tines are withdrawn from the ground surface, the link arms may position the tines in a substantially vertical position for the next cycle of penetration into the ground. Tines are generally cylindrical, are hollow or solid, and produce holes by pulling up plugs or cylindrical cores of soil as the tines move by rotation of the flywheel.
Holes produced by aerator tines may be substantially vertical, and perpendicular to ground surfaces, when ground surfaces are horizontal. However, the holes may not be perpendicular due to undulating or sloped surfaces. For example, golf courses may have undulations or steep slopes in need of aeration. While an aerator travels over undulations or slopes, the coring head may not be perpendicular to the ground surface and, as a result, the tines may enter and/or exit the ground at angles that are not perpendicular to the ground surface. As a result, the holes are not perpendicular to the ground surface, and may have rough edges and be subject to erosion. Additionally, if the tines are not perpendicular to the ground surface, they do not provide uniform hole depth. Nor do the tines provide uniform spacing between the holes.
U.S. Pat. No. 7,293,612 relates to a Walk Aerator with Ground Following Coring Head designed to adjust the vertical position of the coring head relative to the frame in response to changes in ground contour. If the skid assembly rotates sufficiently out of its horizontal position, a pivotal connecting rod attached to the skid assembly causes a switch actuator to depress either of a pair of limit switches. Each limit switch may actuate a hydraulic cylinder to raise or lower the height of the coring head on the frame. As the coring head moves up or down, however, the tines may not be perpendicular to the ground surface.
U.S. Pat. No. 8,255,126 relates to an Aerator having Flexible Frame designed for use on sloped or undulating ground surfaces of golf courses and other turf. The aerator includes a pair of frame sections linked together at a horizontal pivot axis, one of the frame sections supporting a coring head. A ground sensor is pivotably attached to one of the frame sections so that the ground sensor may pivot in response to changes in ground slope and provide output relating to the magnitude of the change. Based on the output, a flex frame actuator pivots the pair of frame sections with respect to each other.
An aerator with a ground sensor may be calibrated before aeration begins to determine the neutral position of its ground sensor. Static calibration of the ground sensor, such as a turf guard, may occur during machine setup, before the aerator is moving or the tines are reciprocating with the coring head. For example, a static calibration routine may obtain a neutral position signal, such as a voltage signal from a potentiometer, from the ground sensor while it is on flat ground.
Once an aerator begins moving and the tines are reciprocating with the coring head, the ground sensor may encounter changes in the ground surface. For example, the ground sensor may pivot up or down, or raise and lower, if there is a slope change. Each signal from the ground sensor that is different from the static calibration's neutral position signal indicates a slope change. In response to the signals, the aerator may shift the coring head to ensure the tines penetrate to the desired coring depth and the tines are perpendicular to the ground surface. The aerator may have a vehicle control unit that stores the static calibration's neutral position signal, compares the incoming signals to the neutral signal, and commands a hydraulic cylinder or an electric or electronic actuator to move the coring head as needed.
However, the ground sensor may pivot up or down, or raise and lower, for reasons other than slope change. For example, the ground sensor may move away from the static calibration's neutral position in response to active forces of the tines reciprocating with the coring head, or active forces of the aerator traveling across the ground surface. Different turf conditions and tine configurations may have different impacts on the movement and position of the ground sensor. The ground sensor may produce position signals that are different from the static calibration's neutral position signal even without slope changes. The aerator then may move the coring head to a position that fails to provide the desired hole depth and/or does not align the tines perpendicular to the ground surface. This is because static calibration routines do not account for the active forces of aeration or the active forces of the aerator's movement over the ground surface.
In response to this problem, mechanical adjustments may be made to the coring head attachment frame in an effort to produce holes having the desired depth and angle. An aerator with active turf calibration of the ground sensor is needed that reduces or eliminates the need for these mechanical adjustments. An aerator with active turf calibration of the ground sensor is needed that may be used in various conditions with consistent results. An aerator with active turf calibration of the ground sensor is needed that allows calibration during an aeration pass. An aerator with active turf calibration of the ground sensor is needed that provides perpendicular holes, consistent depth and improved hole quality. An aerator with active turf calibration of the ground sensor is needed that provides an offset from the static calibration's neutral position.